The invention relates to a diaphragm pump with a diaphragm of elastic material, which, in its reinforced central area, possesses a cavity for the head of a connecting rod having a reciprocating motion which moves the diaphragm between top and bottom dead center points. The diaphragm is secured by its outer rim to the pump housing. In the case of most molded in connecting rod heads, when the corresponding diaphragms are used at elevated pressures, experience has shown that diaphragms in pumps of this type are damaged in a surprisingly short time by developing fissures on their upper side.
The object of the present invention is to create a diaphragm pump of the type mentioned in the above introductory passage, having a diaphragm which can operate for a long period without damage at higher pressure loadings, and, possibly, also higher speeds of rotation, such as, for example, 4,500 RPM of the drive shaft. In case of need, the capability for even a higher pump capacity should be present.
For the achievement of this object, what is proposed is that at least one peripherally disposed rib be provided essentially radially outward from, and proximal to, a central area, which area is bounded by the outline of the connecting rod head or limited by the outline of a part of the diaphragm near to the said connecting rod head.
DE 196 31 081 C1, to be sure, does disclose a diaphragm, which exhibits corrugations on one side, largely to compensate for a compression of the diaphragm material, wherein the deepest points of the corrugations project from the underside of the diaphragm as weak undulations. The compression of the diaphragm material, by these measures, can indeed be reduced or avoided by deflecting the diaphragm in the direction of certain areas. Nevertheless a weakening of the diaphragm has been incurred, since the loss of strength of the material called forth by the relatively deeply impressed corrugations reflected on the other side cannot be compensated for.
Also, U.S. Pat. No. 4,238,992 shows a diaphragm, which has ribs on its reverse side. This diaphragm is provided for a pump which is powered by liquid or air pressure. In order to improve the operational life of such a diaphragm by the use of a material of relatively greater stiffness, ribs are provided on the pressure driven side.
In the case of the present invention, at least one encircling rib, intended as a reinforcement rib, is purposely placed on the front side of the diaphragm, where the forces transmitted into the diaphragm from the connecting rod head spread into the radially adjoining annular area of the diaphragm. By the fact that the rib(s) extend in its circumferential direction in this force transmission zone, where also large bending and loading occurs, a greater structural strength of the diaphragm to counter the pressure is achieved. At the same time, the flexibility of the diaphragm is maintained which acts against fissure formation. Empirical trials have shown, that even under conditions made more severexe2x80x94that is, increased pressure, high RPMxe2x80x94an essentially longer operational life is brought about for the diaphragm, than is the case with diaphragms without reinforcing ribs, at least ribs in the corresponding area.
It is particularly advantageous, if a plurality of concentric ribs are provided, which are radially spaced apart one from the other, and located proximal to the central area of the diaphragm. In this way, a stabilizing effect is brought to the surrounding zone of the especially critical force transmission area between the outline of the connecting rod head and the radially, outward extending annular diaphragm surface. Moreover, because of the force diversion capability of the diaphragm, a greater pump capacity is possible.
The danger of the formation of fissures and general damage decreases in proportion to greater radial distance from the critical force transmission zone near the connecting rod head. This characteristic leads to an additional development of the invention, wherein a multiplicity of circular ribs are separated from one another and accordingly, the separation distances in the central area can be less than the separation distances farther outward.